libansilove: update to 1.2.8.

libansilove 1.2.8 (2020-10-25)

- Add LibFuzzer-based fuzzers for each supported format
- Do not hardcode CMAKE_BUILD_TYPE to "Release" in CMakeLists.txt
- Only enable FORTIFY_SOURCE level 2 for release builds
- Add #ifdef __cplusplus extern "C" to allow calling library functions from C++
- Constify input and output arguments of ansilove_loadfile() and
  ansilove_savefile()

(fcambus)